Gasoline is a mixture of n-heptane and 2,2,4-trimethylpentane (an anti-knock additive), and very small quantities of various other chemicals. 2,2,4-trimethylpentane is an alkane with eight carbon atoms (hence OCTane). The ratio of 2,2,4-trimethylpentane to n-heptane in the gasoline is the "octane" rating.

Ex. 91% 2,2,4-trimethylpentane results in 91 octane gasoline.

Anything over 100 is a mixture of 2,2,4-trimethylpentane and either methanol or ethanol.

GM

 

Because they don't know any better. I'll bet they think their bike is faster running racing gas, when in reality they're hurting their performance.

 

124TQ/110HP, carbed CV44.

 

Very nice,

 

When I first bought my bike the salesman and all my other friends have told me to put the "good Stuff" and its never done me wrong. For the difference in cost.. its worth it. Just my opinion.

 

On a stock spec engine be it a harley a Briggs and Stratton small block you would be correct. Fuel blend doesn't necessarily have to have ethanol blended in to raise octane or anti knock capabilities. Before my time, gas had lead as a top end lubricant and anti knock agent. Can still get leaded race gas through VP.

If you were to take the theory that higher octane gas is a waste, apply this theory with a modern fuel injected car of your choice. For simplicity sake, example will be a 4.8 V8 chevy. On a scan tool you can view the fuel tables per engine operation (open loop closed loop engine load engine speed) you can view that table plus fuel pulse width, engine knock count, ignition advance, misfire data, 02 readings mass air flow readings etc.
take this 4.8 with 87 octane run it, run it hard. Lots of wide open throttle runs up steep hills, load the bed of the truck with say 800 pounds record all the pid data. Now go clean the tank and lines fuel rails of cheap stuff, fill with 93 octane.
You'll notice the knock counts are lower, ignition advance went higher, 02 sensor readings are much sharper. I'm not saying you are going to feel or see a 10-20hp increase in output or even gain that by using higher octane.

But you sure will see a less knock count and a higher ignition advance. More advance typically means more power. Go back to distributor small blocks. Typical 12-15* dwell at idle per a stock spec engine.
My race cars, I would set the engine to 3500 rpm, rotate the distributor to advance to 32-38* I was running 108-115 octane. Compression ratios ranging 10.5-13:1 all dependent upon cylinder volume (bore and stroke) piston profile such as compression height (wrist pin height) how far in or out of the hole using a dial indicator at TDC, combustion chamber volume, gasket thickness etc. simple equations to calculate compression. Put 87 or 93 even in one of those higher compression engines you'd be lucky if it started. May fire on 93 but you'd have to retard the timing drastically, and on a dyno you would see a loss of power when retarding ignition timing. Even when retarding timing to run 93 it may knock, ping, and smoke.

Run whichever fuel you want. I'm a proponent of higher octane fuel. You don't have to buy into Mobil or shells claims of detergents or nitrogen in the higher grades of fuel. But I didn't have the problems my friends had with their higher mileage pickups. My old 5.3 had 172k on it when I traded it in. Ran a Volant cold air intake, no muffler no 3rd cat, was a flex fuel 5.3 07 classic, not the 4cyl mode 5.3 in the new body style 07. That truck never had a spark plug changed, never had any issues drivability wise. Didn't have a tuner on it until the last 2 years I owned it. It only knew 3 modes of operation. Wide open throttle, 60-80mph cruise speeds, and idle. Friends who had that same engine whether stock or cai and exhaust systems running 87 were doing plugs at 80-100k one had a leaking intake gasket (normal wear and tear not a result of running cheap stuff) when the manifold came off I inspected the ports and with a bore scope the back sides of the valves. Lots of carbon build up. When I did the intake gaskets on mine at 145 the valves and ports were very clean, slight discoloration in the ports slight varnish on the valves but nothing like their engines... I'll run 93. My 14 silverado with the direct injected 5.3 suggests 87 or E85. Because of the winter it idled a lot (big no no for direct injected engines that aren't diesels) 1 buddy has the same truck and at 22k miles had to have new heads installed due to such excessive carbon build up it damaged the valve seats and had a nasty top end tick so much so it caused the truck to pull timing until it stalled. He would idle it as much as me but was light on the gas. I run to the floor board all the time. GM hotline advised the techs and writers to inform him to run it wot more often and to run at least a full tank of E85 or 93 octane at least once a month. The problem with direct injection combined with the PCV system, there's no way to "wash the valves" without fuel and air going across them, combine that with oil mist drafting in the intake stream you get a recipe for carbon build up. Ford ecoboost suffer from this too if they aren't run WOT constantly. Lots of less enthusiastic drivers had to have engine repairs in their beloved F150s.

It's for those reasons I am a proponent of Mobil 93 octane.